Normal and abnormal bowel appearance on emergency ultrasound

1. Emergency US:
Bowel Evaluation
Rathachai Kaewlai,MD
Division of Emergency Radiology, Department of Radiology
Ramathibodi Hospital
Emergency Radiology Minicourse 2016 | 28 Jun 2016 12:30-13:30

2. Disclosure of Commercial Interest
I have no relationships
with commercial interests to disclose

3. This talk is adapted from an award-winning presentation at
the annual scientific meeting of the American Society
of Emergency Radiology (ASER) in Boston (2013)

4. Key Points
Transabdominal US has potential to help diagnose and
manage acute GI disorders and mimics
US is most effective when prevalence of the suspected
conditions is high

5. Outline
Introduction
US technique
Normal bowel wall “gut signature”
US of abnormal bowel
Pathologies

6. Introduction
Availability, affordability and speed of US imaging
High level of operator skills and experience
Image fromAmberUSA.com

7. Principles
Most bowel pathologic findings displace bowel gas and
feces, making them stand out against normal bowel
segments
Image fromweb.duke.edu

8. Selecting the Probes
Curvilinear, low freq (3-5 MHz)
Linear, high freq (10+ MHz)
3D curvilinear probe

9. US Technique
Start with curvilinear probe to examine
Area of pain: solid organs, peritoneal fluid
Layout of large bowel
Distribution and motility of small bowel

10. US Technique
Focal bowel masses, segments of wall
thickening and dilated loops may be apparent
on curvilinear probe but require high-
frequency linear probes to identify and
characterize changes in bowel wall layers

11. Graded Compression US
Puylaert originally described this technique in 1986
“Gradual progressive increase in pressure the operator
applies to the probe while making gentle sweeping
movements”
Radiology 1986; 158:355-360

12. Graded Compression US:
Suggested Techniques
Step Probe Area(s) of Scanning Organs Visualized
0 C All 4 quadrants with
curvilinear probe
Any free fluid
1 L LLQ for calibrating scan
parameters
Sigmoid colon crossing psoas and
anterior to iliac vessels
2 L RLQ Find ascending colon
Find IC valve
Find terminal ileum
3 L If found pathology,
specifically scanning this area
Bowel of interest (point of
tenderness or abnormality suspected)
4 L ”Mowing the lawn” Check entire colon
Check entire small bowel
5 L Additional views Bowel of interest

13. First, Adjusting Scan Parameters
Focused examination linear
high-frequency probe may start
in left iliac fossa
Find sigmoid colon
Easily identified
Constant anatomy crossing left psoas and iliac vessels
Adjust scan parameters (depth, gain, focus, etc)
Image fromRadiologyAssistant.nl

14. Scanning Right Iliac Fossa
Find ascending colon
Find terminal ileum (in
continuity with IC valve)

15. Scanning Right Iliac Fossa
If suspicious bowel segment seen, specifically examine
Bowel thickening
Alteration of individual bowel layers
Vascularity
Extraintestinal abnormalities such as thickened
mesenteric fat, interloop fluid, lymph node enlargement

16. Mowing the Lawn
Systematic technique to survey
entire intestine in abd
Overlapping vertical sweeps of
high-frequency probe up and
down the abdomen (manner of
lawnmower)

17. Additional Views
Posterior manual compression
Left lateral decubitus (assess retrocecal area)
Transvaginal
Images from Janitz E et al. J Am Osteo Coll Radiol 2016;5:5

18. Normal Bowel Wall:
Mucus Pattern
Collapsed bowel
containing highly reflective
mucus in its center
Target appearance

19. Normal Bowel Wall:
Gas Pattern
Gas-filled bowel causing
echogenic band with
artifacts underneath
Only anterior part of
bowel wall visualized

20. Normal Bowel Wall:
Fluid Pattern
Fluid/feces-filled bowel
loops

21. Normal Bowel Wall
“Gut Signature”
High frequency probes (15+ MHz)
Five alternating bands of high and low echogenicity
Most easily seen when fluid-filled bowel or ascites
Image fromRadiologyAssistant.nl

22. Normal Bowel Wall
“Gut Signature”
Layer 1 Superficial mucosa Fine bright line
Layer 2 Deep mucosa Gray
Layer 3 Submucosa Bright
Layer 4 Muscularis propria Dark
Layer 5 Serosa Fine bright line
Image fromRadiologyAssistant.nl

23. Normal Bowel Wall
“Gut Signature”
At least two most prominent layers are evident due to
relative thickness and high contrast
Bright submucosa (Layer 3)
Dark muscularis propria (Layer 4)
(Layer 2 is lost among luminal contents)
Image fromRadiologyAssistant.nl

24. Normal Bowel: In General
Up to 2-3 mm thick varying on contraction, relaxation
No Doppler signal in normal bowel wall
Healthy bowel can be compressed and shifted by probe
pressure (limited compressibility in obese individuals)
Kralik R et al.Gastroenterol Res Pract 2013, article ID896704
Terminal ileum without and with compression

25. Normal Bowel: SB vs. Colon
Features Small Bowel Colon
Location Central Peripheral
(picture frame)
Appearance Folds (lesser distally) Haustra
Contents Fluid or dry
Minimal air
Feces
Air
Spontaneous peristalsis Should be seen in
healthy segments
Rarely
Easy to compress and
displace by US probe
Yes, easily Yes for mesenteric
segments

26. US FINDINGS OF
ABNORMAL BOWEL
Wall thickening (m/c, most striking)
Altered gut signature
Narrow or dilated lumen
Plasticity, mobility, peristalsis
Altered blood flow
Extramural changes
Mesenteric lymph node

27. Bowel Wall Thickening
Focal, segmental or diffuse
Circumferential or partially circumferential
Target sign, ring sign, pseudokidney sign
Edema, hemorrhage, inflammation, tumor or other
infiltrations

28. Wall Thickening:
Tumors vs. Infection/inflammation
US Features Tumors Infection/inflammati
on
Length of involvement Short Long
Thickness More (usually >1 cm)
Irregular
Less except ischemia
Smooth
Circumference Yes,asymmetric Yes,symmetric
Gut signature Lost Preserved (not always)
If absent,suggest ischemia
Vascular flow Increased,high RI Increased,low RI
If absent,suggest ischemia

29. Altered Gut Signature
In diseased segment, bowel layer pattern may be
Preserved
Exaggerated
Distorted
Diminished or obliterated

30. Bowel Lumen: Dilatation
Aneurysmal dilatation (mostly seen in lymphoma)
Dilatation proximal to obstructing lesion: initially with
increased peristalsis, later without peristalsis (DDx
paralytic ileus)
Images from UltrasoundCases.info

31. Bowel Lumen: Narrowing
Narrow lumen 2/2 thickening or stricture

32. Bowel Plasticity, Mobility and
Peristalsis
Most diseases stiffen bowel segments
Rigid
Less compressible
Less easily displaced
Reduced or absent peristalsis
Tethering, architectural distortion with reduced
peristalsis suggest more chronic or aggressive process
such as transmural inflammation or malignancy

33. Bowel Non-compressibility
Lack of compressibility may be
due to appendicitis,
intussusception, bowel
malignancy or luminal distension
from obstruction
Cystic or hypoechoic mass DDx

34. Altered Blood Flow
Normal bowel wall perfusion
cannot be demonstrated by
color or power Doppler
Presence of flow =
pathologic perfusion (eg,
hyperemia in actively
inflamed segments)Appendicitis

35. Superb Microvascular Imaging
(SMI)
Algorithm based on Doppler signals
Separate flow signals from overlaying tissue motion
artifacts by removing global motion signals
Images from Sara O hara, Toshiba Inc

36. Extraluminal Changes
Bowel wall disease may involve adjacent loops or solid
organ, or result from external disease
Peri-intestinal fluid, collections, abscesses, fistulas
Altered mesenteric fat

37. Extraluminal Changes: Fluid
Septated fluid collection 2/2 malignant peritoneal disease

38. Extraluminal Changes: Free Air
Thin echogenic line with
posterior reverberation
between abdominal wall and
anterior hepatic surface
Left lateral decubitus
Shifting in real time

39. Fat Stranding
Increased fat echo
In RLQ,this is 73%
sensitive and 98% specific
for inflammatory disease
Compare with
contralateral abdominal
fat echo

40. Mesenteric Lymph Node
Size
Shape (oval or round)
Echotexture (hyperechoic or hypoechoic,
heterogeneous)
Smooth or irregular surface
Conglomeration or matting
Images from UltrasoundCases.info, case 496

41. Valsalva Maneuver
Help detect hernias of bowel, mesentery and omentum
Intermittent hernia – show reducibility
Contiguity of mass with intraperitoneal space
Better depiction of hernia sac or abdominal wall defect

42. Transvaginal Imaging
Deep position of appendix
Terminal ileitis
Sigmoid/rectal inflammation
Pelvic masses or abscesses

43. PATHOLOGIES
Appendicitis
Diverticulitis and epiploic appendagitis
Obstruction and hernia

44. Appendicitis
Most common emergency surgical condition
Luminal obstruction usually by fecalith or appendicolith
Luminal distension, mucosal ischemia and necrosis
Bacterial invasion, transmural inflammation, full-
thickness infarction and perforation
Image from PathologyOutlines.com

45. US of the Appendix
Thin, blind-ending tube with typical gut signature
Continued with cecal pole
Rising 1-2 cm below ileocecal valve
Variable length (average 8 cm, range 1-24 cm)
Location (m/c pelvic/descending and retrocecal)

46. Acute Appendicitis: US
Non-compressible
Maximum outer diameter >6 mm
Use of threshold alone cautioned -
not always true (normal appendix
can be >6 mm, filled c feces and air)
Sensitivity 100% but specificity 68%

47. Appendicolith
Appendicolith not reliable of
inflammation

48. Strategic Approach in Imaging
Appendicitis
Prospective comparative studies of CT and US in acute
appendicitis favor CT
Graded compression US SE 78, SP 83
CT SE 91, SP 90
US-first strategy issues with unavailability of skilled
operators within acceptable timeframe. However, US
does not increase perforation rates or delay surgery

49. Issues Ahead
Paradigm shift to ATBs Rx of
uncomplicated appendicitis
would shift burden of
imaging to identifying those
cases with complications
WebMD

50. Mimics of Acute Appendicitis
Gynecologic causes
Acute diverticulitis
Epiploic appendagitis
Mesenteric adenitis
Ovarian or paraovarian cyst 17
Gastroenteritis 14
Cystitis 9
Hemorrhagic ovarian cyst 6
Inflammatory bowel disease 5
Pyelonephritis 4
Nephrolithiasis 3
Obstructing ureteric calculus 3
Ruptured ovarian follicle 3
Colitis 3
Intussusception,hydrosalpinx,hip
effusion,SBO, cholelithiasis
1
each
Trout AT et al. Pediatr Radiol 2012

51. US of Acute Appendicitis:
Ramathibodi Experience
N=238, 72% positivity rate
50% likely appendicitis at US. Of
these, 91% went to OR wo CT
41% of US – non-visualized
appendix. Of these, 51% had
appendicitis
7% of US – alternative dx
Kaewlai R, LertlumsakulsubW,Srichareon P. Ultrasound Med Biol
2015;41:1605

52. US of Acute Appendicitis:
Ramathibodi Experience
For ”non-visualized” appendix at US,Alvarado score
most helpful factor to determine risk of appendicitis
If Alvarado >/=7, almost all would have appendicitis
If Alvarado 4-6, 2/3 of cases would have appendicitis
Our CT performance (Trimankha P et al.unpublished data)
SE 89, SP 90, PPV 87, NPV 91, accuracy 89

54. Colonic Diverticulosis
Most colonic diverticula “false diverticula”
Prevalence increases with age (>50% of >70yo)
M/C sigmoid colon
Vary in size from tiny intramural, transient to
permanent protrusion up to 2-3 cm

55. Acute Diverticulitis
Retention of fecal matter within diverticulum causing
abrasion, infection/inflammation of wall, abscess,
perforation
Incidence of diverticulitis increases with duration of
diverticulosis
Image frommedlibes.com

56. US of Diverticulosis
Bright “ears” out with the bowel wall
and acoustic shadowing
Thin diverticular wall with reduced
gut signature
Echogenic band traversing hypoechoic
thickened muscularis propria
Images from UltrasoundCases.info

57. US of Diverticulitis
Protrusion from colon wall
Ill-defined margin
Surrounding echogenic
noncompressible fat
Loss of wall signature

58. Dilated, Fluid-filled Loops
Identification
Which loops are dilated?
Only small bowel dilatation or large bowel as well?
If small bowel dilates, is it localized or diffuse?
Peristalsis: increased (early obstruction) or lacking (ileus
or late-staged obstruction)

59. Images from UltrasoundCases.info
Small bowel ileus

60. Take Home Messages
Steps in performing graded compression US (0 to 5)
Use high-frequency linear probe for thin patients
Gradual compression!
Look at bowel in all quadrants, not just the site of pain

61. Special Thanks
Drs Orachart Udompanich and Kamonporn Limchavalit,
Bumrungrad International Hospital for providing several
cases
Dr Sirote Wongwaisayawan for preparing the detailed
information of diseases
Dr Ruedeekorn Suwannanon for nice graphics

62. THANK YOU FOR
YOUR ATTENTION